Will the new excavations at Stonhenge unravel the mystery of the stones? © English Heritage

Archaeologists working on the first excavation within the stone circles at Stonehenge since 1962 are once again attempting to unlock the secrets of the ancient monument by finding the foundation holes of the very first stone circle, built more than 4,500 years ago.

The excavation, which is being led by Professor Tim Darvill of University of Bournemouth and Professor Geoffrey Wainwright, President of the Society of Antiquaries, aims to provide a more precise dating of the Double Bluestone Circle, which was later dismantled and re-erected.

Due to take a fortnight to complete, the work will draw on newly developed techniques to date fragments such as antler bone tools and organic matter such as pollen grains and shells as well as fragments of the original blue stone pillars. The findings will then help archaeologists to accurately date the original monument.

Experts will also compare the new bluestone sample with those obtained in the last few years around the source of the original bluestones: in the Preseli Hills in southwest Wales. This will help to illuminate the mystery as to when and how at least 80 such stones were brought to Salisbury Plain 250 km away nearly 4,500 years ago.

“The bluestones hold the key to understanding the purpose and meaning of Stonehenge,” said Dr Simon Thurley, Chief Executive of English Heritage. “Their arrival marked a turning point in the history of Stonehenge, changing the site from being a fairly standard formative henge with timber structures and occasional use for burial, to the complex stone structure whose remains dominate the site today.”

The bluestones hold the key to understanding the purpose and meaning of Stonehenge. © English Heritage

Experts have come up with various theories as to why the bluestones used in Stonehenge’s earliest structures were transported 150 miles (250 km) from southwest Wales to their present location on Salisbury Plain. Further seemingly boundless conjecture has surrounded the original use of the monument.

“This small excavation of a bluestone is the culmination of six years of research which Tim and I have conducted in the Preseli Hills of North Pembrokeshire and which has shed new light on the eternal question as to why Stonehenge was built,” explained the dig’s co-leader Geoffrey Wainwright.

“The excavation will date the arrival of the bluestones following their 250 km journey from Preseli to Salisbury Plain and contribute to our definition of the society which undertook such an ambitious project. We will be able to say not only why but when the first stone monument was built.”

The excavation at Stonehenge will last for two weeks until April 11 2008. During this time Stonehenge will be open as normal and visitors will be able to observe up close the excavation as it happens on plasma screens inside a special marquee.

Find out more information about the progress of the dig at the English Heritage website